When electromagnetic conducted noise that has been propagated through power cables and communication cables enters ICT equipment, communication problems such as equipment malfunction and frame loss occur. When measuring the voltage with respect to the ground plane of the conducted noise, if the measurement instrument cannot be grounded within the measurement site, it is difficult to accurately measure the voltage of the conducted noise. In this paper, a new method to measure voltage with respect to the ground plane of conducted noise was proposed.

This paper introduces a method to correct the voltage and waveform of conducted noise measured without grounding. If the capacitance between the ground of the measurement instrument and the ground plane can be accurately estimated, it is possible to correct inaccurate measurement results taken when the instrument is not grounded into accurate measurement results measured when the instrument is grounded. In order to measure this capacitance, a ground capacitance estimating device consisting of electrodes facing the ground plane, an oscillation circuit, and a voltage measurement circuit is proposed in this paper. The electrodes of this device form capacitance between the electrodes and the ground plane, and the voltage measured by the voltage measurement circuit changes according to the capacitance when the signal is output from the oscillation circuit. This feature is used to estimate the capacitance formed between the ground of the measuring instrument and the ground plane. In order to verify the proposed method, the capacitance between the oscilloscope ground and the floor of a shielded room is derived, and the square waveform, which is sagged due to the lack of grounding, is corrected by using the derived capacitance. As a result of verification, it was shown that the proposed method can estimate the capacitance and can correct the ungrounded measurement results using the estimated capacitance.

The measurement method of conducted noise introduced in this paper is expected to contribute to the troubleshooting of communication problems caused by conducted noise in ICT equipment, which is expected to increase in the future. This paper is highly useful and deserves the Best Paper Award.